The clinical core stable isotope ratio mass spectrometry core laboratory was started to support all stable isotope applications in the clinical labs. In our 1st full year with our 2 IRMS systems installed, there has been tremendous progress. The first clinical doubly labeled water has been completed. Several new DLW studies are underway with Monica Skarulis, Kong Chen and Kevin Hall. Research continues towards analysis of minute samples for DLW studies. Metabolic tracer studies are about to begin. We have been preparing for numerous stable isotope tracer studies. Deuterium and 13-carbon glucose methods have been developed. Kristina Rother, Rebecca Brown, Bernard Miller and Anne Sumner will all be starting glucose tracer studies in the next few months. We developed a method for the analysis of 3-O-methyl glucose for a study that Kristina Rother and Rebecca Brown are starting. We are developing a method for labeled free fatty acids for studies that Bernard Miller and Anne Sumner are planning.